Can't get that tension right!

We started our afghans from crochet class last night, and I sure hope I can see this project through! Crocheting an afghan as a first project is pretty daunting. We practiced the basic stitches first for a while at class on a swatch, then moved on to our "real" yarn for the afghan. What I learned is that the reason my crocheting was always curved when I tried to do it is that I crochet my base chain way too tight (ridiculously and embarrassingly so!), so I tried crocheting the base chain with a larger hook, and it seemed to work rather well. But I sure can't get that tension right. I'm holding the yarn the way the instructor showed us, but there are bits here and there that aren't perfectly uniform. This seems trickier to me to get right than knitting, but maybe I just need lots of practice to get it right. To be sure, I'll get lots of practice crocheting a whole afghan! I sure hope I can finish this project and don't get discouraged. I'd hate to have to return all that yarn or have it go to waste.